Safeworking Equip

Safeworking Equip

There are two methods of safe working in use on the BBR.

STAFF & TICKET

Staff and ticket is the safe working method employed on the Bushland Loop.

The driver must be in possession of the staff for the section at any time his train is outside the Whiteman Village Junction station limits.

If two trains are to travel in the same direction on the Bushland Loop, a ticket is issued by the signalman indicating the date and time of issue and type of train. The ticket is given to the driver of the first train who accepts it providing he is shown the staff for the section. The driver of the second train receives the staff with a copy of the ticket attached.

ELECTRIC STAFF

Electric staff is the safe working method employed on the Mussel Pool line.

Large electric staff instruments are located in the Mussel Pool and Whiteman Village Junction signal cabins. The driver must be in possession of a staff for the section any time his train is outside the station limits of Mussel Pool or Whiteman Village Junction.

There are a total of 16 staffs housed in the staff instruments. If the line is clear, a staff is withdrawn from the instrument and given to the driver. Once a staff is removed from either instrument, both instruments are locked and no other staff can be removed. When the train reaches the other end of the section, the staff is returned to the instrument at that end and both instruments are unlocked indicating the line is clear. Another staff can then be removed.

HOW IT WORKS

The staff instruments at Mussel Pool and Whiteman Village Junction are electrically connected by one pair of wires of the open aerial pole route between the signal cabins. At each end there is a battery providing power to the instruments.

When the line is clear, the batteries at each end are connected in opposition. There is no current flow over the pole route and the galvanometer needle on each instrument is vertical indicating the line is clear.

To remove a staff, two electromagnets in the instrument need to be energised in the same direction to lift the latch enabling a staff to be removed.

As the staff is moved into the gate, the local battery energises one electromagnet (local coil) and the battery at the other end energises the second electromagnet (line coil). If the line is clear, both coils lift the latch to enable the staff to be removed. Removal of the staff reverses the electrical connection between the instruments and current flows over the pole route. The needle in the galvanometer on each instrument is moved to 45 degrees indicating the line is occupied.

A second staff cannot be removed as the current through the line coil and local coil are in opposition preventing the latch from being lifted.

If the aerial pole route is broken, a staff cannot be removed as only the local coil is energised and this is insufficient to lift the latch.

Electric staff was used extensively throughout the WAGR system. The BBR electric staff is the only working installation now in WA.

Webmaster N. Blinco